Art of obtaining chlorates by electrolysis.



"NIL 665,426.

W. T. GIBBS.

ART 0F OBTAINING GHLORATES BY ELCTRULYSIS.

(Applicaticu med sept. 9, 1895.)

(No Model.)

Patented 1an. 8, l90i.

2 Sheets-Sheet l.

No. 665,426. Pa'tenied lan. 8, IQOI. W. T. GIBBS.

ART 0F DBTAINING CHLORATES BY ELECTROLYSIS.

(Application led Sept. 9, 1895.) (No Model.) 2 Sheets-Sheet 2.

UNITED- STATES PATENT OFFICE.

WILLIAM T. GI'BBS, OF IEUCK'INGHAM, CANADA, ASSIGNOR, BY DIRECT ANDMESNE ASSIGNMENTS, TO THE NATIONAL ELECTROLYTIC COMPANY, OF

N EW' YORK.

ART jOF OBTAINING CHLORTATES BY ELECTROLYSIS.

SPECIFICATION forming` part ofl Letters Patent No. 665,426, datedJanuary 8", 1901.

Application tiled September 9, 1895.

lTo all whom it may concern,.-

Be it known that I, WILLIAM T. GIBBs, a British subject, residing' atBuckingham, county of Ottawa, Province of Quebec, Do-

minion of Canada, have invented certain new and useful Improvementsinthe Art of Obtaining Ohlorates by Electrolysis, fully described andrepresented in the following specification and the accompanyingdrawings, forming a to part of the same.

My invention relates to the production of chlorates from the chlorids ofalkaline and alkaline-earth metals, and has for its object increase inthe efficiency and economy of such processes. In these processes thisdifficulty has been encountered and has proved very serious. Inasmuch aswhen a solution of mixed salts is submitted to electrolysis every saltpresent is to a greater or less extent de;

so composed, that salt, the production of which is the object of theprocess, will, as it accumulates in the liquid, be itself to a certainextent decomposed by the action of the current, and a portion of thecurrent will thus a5 be wastefully consumed. It has been usual tocontinue the electrolysis until the saturation of the bath .became suchthat crystallization would occur in the cell itself or in anotherreceptacle into which the liquid was 3o drawn oi and allowed to standfor that purpose. As the percentage of the salt in the bath increasedthe percentage of current wasted in attacking it also increased and theecieucy of the process diminished. While,

3S. therefore, the efficiency at the beginning might be good, that atthe end was very low and the average showed a very large percentage ofloss.

I have discovered that by making the dow 4o of the liquid through thecell continuous it becomes practicable to remove the salt from the bathrapidly and continuously and while its percentage is still small, andthereby to greatly reduce the quantity of current lost in uselesslydecomposing it. Thus whereas the degree of saturation usually heretoforeemployed ln the practice of such processeshas been upward ot' tenpercent. that employed in my process may be less than three per cent.,

Serial No. 561,911. (No specimens.)

and as a consequence the eiciency of the elec- 5o trolysis is nearlydoubled. Having removed 'the chlorate from the liquid, I replenish itwith chlorid and return it in a continuous stream to the cell. I havealso discovered that the chlorids of the alkaline and alkalineearthmetals can be electrolytically treated between metal electrodosseparated from each other only by the solution andthe necessaryinsulation-i. e., without the use of a separating-diaphragm--witheconomy and suc- 6o cess. It has been heretofore supposed that thehydrogen freed at the cathode would reduce or prevent the formation ofthe chlorates unless the electrodes were kept separate by a diaphragm orunless the hydrogen were consumed at the cathode-as, e. g., by an oxidof copper electrode. It has also been considered desirable to thusseparate the liberated hydrogen and chlorin to prevent the formation ofhydrochloric acid and conse- 7o quent diminution of the amount ofchlorate produced. I have, however, discovered in the course of myexperiments that these rev actions do not occur in a substantiallyinjurious degree when the percentage of chlorate is kept down to a lowpercentage by a continuous fiow of the solution through the cell andthat as a consequence I can employ metal electrodes in close proximitytoeach other. This is a great advantage, since the use of a 8o diaphragmlargely increases the resistance of the electrolytic cell, andconsequently the expense of the production', while the use of anon-metallic electrode which will consume the hydrogen is attended withdisadvantages which seriously interfere with the economy of the process.This discovery enables me to construct a cell having peculiaradaptations for my continuous process, I am enabled to place theelectrodes in close and immediate 9o proximity, and thus to use a,current of large amperage and low voltage. The cell in which theseelectrodes are contained is necessarily of small cubical capacity, sincethe latter cannot be greater in proportion to the electrodesurface thanwill properly feed the electrodes by the action of diffusion, andtherefore it is not adapted to the old discontinuous proces.

In the lirst place its capacity is so small that the filling of thecell,the application of the current, and the emptying and the refillingof the cell would entail inconvenience which would makesuch use almost,if not wholly, impracticable, while if the solution passes through thecell in a continuous flow its capacity is ample.

Another very important advantage secured by the small size of the celland the large amperageor density of the current Iam enabled to use isthat I can produce all the heat necessary to raise the temperature tothe proper poin-t for the decomposition of hypochlorites by the actionof the current itself. Heretofore it has been usual on account of thelarge capa-city of the cell employed in the man ufac'- ture of chloratesto supply this temperature by meansof heat from an external source. Thisis very dilcult to do practically because of the necessity of usingapparatus for conveying the heat of the solution which will be resistantto the action of chlorin. In this connection, again, the continuous flowof the solution, through the cell.is of great consequence, for thereason that the large amount of current I am enabled to use in the smallcell would, if the electrolysis were conducted in the usualdiscontinuous manner, heat the bath much higher than is permissible,while the continuous flow of the solution reduces and limits thedevelopment of heat to such a degree as is desirable for theprocess-namel y, within the limits of 90 to 200 Fahrenheit, thepreferable temperature being from` 110 to 120 Fahrenheit, With thisconstruction of cell and with a continuous flow I am enabled to use acurrent of two to four (preferably three) amperes per square inch ofelectrede-surface, which very greatly increases the capacityof the plantin proportion to its size over anything heretofore accomplished.

Another important advantage secured is that I am able to control andregulate the temperature of the solution in the cells by regulating theflow of the solution, which as it enters the cell is cold and causes anoverflow of the hot solution. This is a much more convenient means ofregulating the temperature than by regulating thesupplyof extern al heaton the one hand or than by regulating the density of the current used onthe other hand, and this advantage is of greater value where a batteryof cells such as is especially adapted to my'process is employed lthanwhere single c ells are used, for this reason, that where a singlecurrent is directed through a battery of cells if it were attempted toregulate the heat in the cells by changes in the density of current allthe cells would be affected by each change, whereas the temperature ofthe 'solution in different cells may be dilTerent, owing todifferentconditions of locations of the cells in the battery or differentinternal conditions in the cell or in the supply and delivery pipesleading to and from each cell. The flow of the solution through eachcell, however, can

stance, platinum.

be separately and conveniently controlled, so as to properly limit andadjust the temperature in each cell separately from and inde-v'lpendently of the others.

As regards the feature of my invention which consists in reducing,limiting, or regulating the temperature of the cell by means ofcontinuous flow of thesolution I intend to claim the same broadly,whether the source of heat be the" current itself "or wholly or partlyexternal to the cell. I have also devised a peculiar construction ofcell specially adapted for the production of thesechlorates andpreferably used'in carrying out my process. l It is necessary in thesecells to use as an anode a lmaterial which is substantially resistant tothe action .of chlorin-as, for inf The cost of this metal or equivalentmaterial, however, makes impracticable the use of heavy sheets aselectrodes, and the high resistance of platinum also unfits it for.usealone as an anode. It is also extremely diliicult to use thia'sheets ofplatinum as electrodes, owing to their tendency to bend and warp, andconsequently shortcircuit. It is also disadvantageous to use compoundplates made up of a cheap metal, which would, if used alone, be subjectt'o disruption in the presence of chlorin plated or covered withresistant material, as platinum, for the reason that it is dillicult tomake such covering at the angles of the plate impervious to the actionof chlorin, and such plates when used have been found to have lessdurability than is desirable. Furthermore, whatever the material of theelectrodes the use of the usual connecting-rods causes much trouble andexpense, since they are both inconvenient in themselves and continuallyliable to disintegration through accidental contact with the chemicals.I have overcome these diliiculties by using for one side of each cell aplate of cheap metal-as, for instance, lead faced with platirum orother` substance substantially resistant to the action ofchlorin-causing the plate and facing to project beyond the other partsof the cell which inclose the solution, so that only the plain face ofthe plate will be exposed to the solution, and employing this platinumface as the anode of a single pair of electrodes contained in the cell,this being my preferred construction, it being understood that I do notlimit myself to it. This facingof platinum or other resistant substancecan be made very thin without disadvantage, since strength and rigidityare supplied to it by the metal backing, which cannot be reached by thesolution. The dif- IOO iiculty of making connections is also avoided,

since these are made through the wall of the cell, and the cell or cellsbeing preferably closed and arranged as described. chemical attack uponparts of the circuit other than the electrolyte is avoided. I have alsodevised a feature of. construction which practically overcomes anotherdilculty ordinarily encountered in such processes-viz., polariverticalwires or metallic rods electuallyl prevents polarization, The bu bblesof hydrogen` 'being spheres have the least-possible contact with tilecylindrical surface of the wires or rods. Consequently they do notadhere there- `rto, bu't'roll up the wires tothe top of the cell andthere escape. In order to obtain theA best results, these rods should beof metal 4 and of small diameter, sincethere is no other material thanmetal whichis equally suitable for the purpose, and if the diameterofthe rods be large the surface approximates to a plane surface and has -atendency tohold the bubbles of hydrogen. I have found'tlle best resultsto be secured by a small rod or wire,

by which I mean a rod or wire having a diameter less than a quarter ofan inch.

In order to facilitate the building up of a series or combination of4cells which. shall have any desired capacity, I cause the metal 'platewhich .serves as the backingfor the lmeans of-'an insulating-gasketentirely separ.construction has greatradvantagesuin con anode ofy onecell to serve as the rea-r wall of another cell placed in contacttherewith, and

to simplify and protect the connect-ions I providein each cell auinterior metallic connection between each cathodeand this rear wall ofthey cell, as by lining the interior of the cell between the two inwhole or in .part with metal or making this part of the cell entirely ofmetal, providing mere conducting'c'onnections between the Vcathode'andthe rear wall.

VIt will of course .be understood thatsuitable videdA with metallicconnections, ,as above.

rating those parts ,of Ithe celiycon-nected with the two electrodes,respectively, and held in.

place by a proper'fastening or clamp.-placed upon the .cell or series ofcells.. By. this constructionl secure a unit for use in constructing aseries of cells, such unitc'ontaining an anode and a cathodebelonging,respectively, to adjacent--pairs of eleetrodes,whichnni`tswhen combined with 'interposed insulatinggaskets constitute fa seriesofcells in=which the path of the current lies entirely throughv the.electrolyte and -t-hey ce-llwalls, exterior connections beingwhollydispensed with, el;` cept at the tweextremites of the series. rThis Vvenicnce'anddurability.

In 'tixed- -awings annexed, Figure lrepres sente a verticalcross-section 'of a seriesoff cells made in accordance with ,myinvention :and set. upv4 for. use'. .-Eig. .2- is -a side elevation ofone .ofthecells-iseenon line 22.01" liig.y 1,-

"the-point of-view;A beiuglto the leftfof Fig. 1';

cell preferably used in carrying out my proc ess. Each cell consists ofa frame A, (shown in vertical cross-section in Eig. l and in sideelevation in Fig. 2,) which may befof instal, but which I prefer to makeof wood, with metallic or other conducting resistant lining B, as shown,or which may be of other material not subject to, attack by thesolution. Upon one side ot' y this frame are attached the rods or wiresC, constituting a. cathode, and on the other side ametallic plate D,faced with platinum E, constituting au anode. The cathode may be ofcopper, zinc, or other suitable metal, as likewise may be the liningr Band the plate D. I prefer copper for the cathode and lead for the liningand the plate. -It should be observed that itis not essential that thelining B be continuous over the entire surface of theframe A, it-beingsufficient if. conducting connection is made between, the cathode andplate D, and the mal electrolytic process, and vents H are provided atthe tops of the cells for the discharge there- "of and of the liberatedgas. In .order that the cells may .be kept always llull, these vents are.placed just above the inside level'oi" the top ofv each cell, the framebeing recessed foi-.that

les

purpose, and, this recessie continued inward,

asshown in' dotted ylines in Fig. 2, in order to permitaccessvofthe'solution to the tenti When .erected for use the framesare 'placedside by side, with a gasket betweenn each two, as shown in Fig. l,-andare lpreferably clamped together by means of. two end plates JK-,con-

' nected by bolts L. The platesJ K are separated from the cells byinsolatingmaterial. The left-hand cell of the series is closed by a4simple plate m, faeed with. platinum. The

platinum face on the metal back handcel-lis omitted. Each -pairoielectrodes is separatedby the corresponding gasket. To-prevent short-cirof .the right- .ouiting by bending of the wires,.horizontalyinsulating-irods O are provided between the electrodes,these`rods.being. supported by .ourvedportions of the wires, or othersuitable supporter other appropriate insulating means mn'ybeemployed. l

Referring nowzto' the diagram Fig.3,. P represents the electrolysiscells "overflowing into. 'coolingchamkers QQ', which maybe one', two, ormore innumber. l 'Il1ese cooling- IIO ' paratns.

chambers are shown as provided with coolingcoils R. The use'of suchcoils is an advan-` tage, since it secures the precipitation of agreater proporticn'of the chlorate in solution; but their use is notessential to my-process. S is a pump for returning the depleted so1ution to the replenishing-vat T,where it meets a fresh supply of chloridand is fed by the siphon X or other connection again into the cell.

The flow of the solution through the cells is, as I have stated,continuous, and the rate of flow and quantity of electric current usedare so proportioned that the solution as it leaves the cell shall-have asmall percentage of chlorate. This percentage is preferably less thanthree .per cent., and I have found the results to be excellent when itwas as low as one and one-half ,to one and three-quarters per cent.

The capacity of the cell advantageous for use in my process is from twoto four cubicinches per squarev inch of electrode-surface. If a greateramount of liquid in proportion to the electrode-surface is present inthe cell, it

is diicult to maintain the requisite degree of heat by the action of thecurrent, and the application of external heat to thecell is difiicultand expensive, and, further, the pres ence of a larger amount ofsolution than that indicated interferes with the proper diffusive actionin the cell. are preferable, I do not limit myself to them.'

By the term close proximity of the electrodes I intend to indicate theclosest prox.

imit'y which it is practicable to obtainbetween insulated electrodes-as,for instance, one-sixteenth to one-eighth of an inch. I do not, however,limit myself to such close'proximity except in those claims in which'the electrodes are specified as being in close proximity.

It is an advantage that tue now ot the liquid should,be continuousthrough the crystallizing-chambers and the replenishing-vat back tothecell, as well as through the cell` itself; but continuous flow is notessential to this part of the process, and I intend to claim lin thispatent the feature of continuous flow through the cell whether or notsuch flowI is continuous through the remainder of the ap-l I do not, ofcourse, limit myself toany special dimensions of apparatus; but I maymenj tion that I have found a convenient size for the cells to betwenty-six by eighteen inches with a thickness of three inches, theelectrodes being about one-eighth of an inch apart. v 4

The action ot the apparatus as above described is that adapted to themanufactu of.A potassium chlorate and other Vchlora which are lesssoluble in waterthan the corresponding chlorids. i sodium'chlorate andof such -other chlorates as are more soluble than the correspondingchloride the separation of the chlorates is ef- While these dimensionsIn the manufacture of` ,saam

f ected by causing the chlorid to crystallize in the cooling-vata andthe subsequent evaporation of the chlorate solution,a continuous fiow ofthe electrolyte being maintained through the electrolytic cell or cells.

It will be understood that the present 1nvention is not limited to theuse of apparatus of the speciiicform shown and described, but 'thatwhile the use of such apparatus is pre-1 ferred the carrying out of therocess claimed herein by any other suitable crm of apparatus is withinmy invention.

The vcell and series of cells shown and described herein form thesubject-matter of another application filed October 8, I1900, Serial 1.The process of obtaining chlorates from the chloride of alkaline oralkaline-earth metals which consists in subjecting the chlorid ihsolution while flowing continuously throughja 4cell to the action of anelectric current betweeix` two electrodes insulated from each other, but

otherwise separated only bythe liquid, the. density of thecurrent usedbeing such as to maintain the solution in the cell at a temperaturesuitable for decomposing hypcchlorites,

'substantially as set' forth.

y2. The process of obtaining chlorates from the chloride of alkaline oralkaline-earth metals which consists in subjecting the chlorid insolution while flowing continuously through a cell' to the action of anelectric current between two electrodes in close proximity and insulatedfrom each other, but otherwise separated only bythe liquid, the density'of-the current used'being suchas to maintain the f solution in the-cellat a temperature suitable for decomposinghypochloritos, substantially asdescribed. '3. The process of obtaining chlorates from the chloride ofalkaline or alkaline-earth metals which consists in subjecting thechlorid in rio solution while flowing continuously through a cell to theaction of au electric current between two electrodes insulated from eachother, butotherwise separated only b'y the liquid, the density ofthecurrent used being such as to maintain the solution in the cell atatemperature high enough for the decomposition of 4 hypochlorites, andthe fiow of solution being.

stautially asset forth.

such as'to prevent thetemperature from rising.

above 200 Fahrenheit or thereabout, sub- 'up' 4. The process ofobtainingchloratesfrom the chlorids of alkaline or alkaline-earth metals whichconsists' in subjecting the chlorid in solution while owingcontinuously'through a cell to the vaction of an electric currentbetween two' electrodes insulated from each other, but otherwiseseparated only bythe liquid, the density of the current used .being suchas to maintain the solution at a tempera ture high enough for thedecomposition of hypochlorltes, and col'ltrollng'he wmpl'iill of thesolution in thecell by regulating thel flow of the solution,subtantiallyasy set forth.

45. The process of obtaining chlorates from the chlorids of alkaline oralkaline-earth metals which consists in subjecting the chlorid in.solution while liowiug continuously through each of a series of' cellsto the action of an electric current passing through the cells inseries, between twoelectrodes in each cell insulated from each other,but otherwise separated only by the liquid, the /den'sity of the.current used being such as to maintain the solution in all the cells ata temperature highl enough for the decomposition-of hypochlorites, andcontrolling the temperature of the solution in each separate cell byregulating the flow of the solution, substantially as se forth.

6. The process of obtaining cnlorates troni the chloride of alkaline oralkaline-earth metals which consists in subjecting the chlorid insolution-while flowing continuously through a cell to the action of anelectric current, between two electrodes insulated from each other, butotherwise separated only by the liquid, the capacity of the cell beingfrom two to four cubic inches per square inch of electrode-surface, andthe current employed bev lng from two to four amperes per square inch ofelectrode-surface, the density of the cnrrent and the liow of the liquidbeing so adjneted that the solution is maintained at a temperaturesuitable for the decomposition' of hypochlorites, substantially as setforth.'

7. The process of obtaining chlorates from the chlorids of alkaline oralkaline-earth metals which consists in subjecting the chloridinsolution 'in a cell to the action of an electric current. between twoelectrodes insulated 'from each other, but otherwise separated only 'bythe liquid, imparting heat to the solution in the cell by suitablemeans, and reducing the temperature of thesolution by maintaining thecontinuous iiow thereof through the cell, whereby is maintained in thecell a,tem perature suitable. for the decomposition of hy'pochlorites,substantially as described.

8. The process of obtaining chlorates from the chloride of alkalineA oralkaline-earth metals which consists in subjecting the chlord insolution while iiowing continuously through a cell to the action ot' anelectric current between two electrodes insulated from' each other, butotherwise separated only by the liquid, imparting to the cell bysuitable means heat sulicient to raise the temperature of the solutionto a degree high enough for the decomposition of hypochlorites, andregulating the temperature 'by regulating the flow of the olultionthrough the cell, substantially as set ort 1.

9. The process of obtaining chlorates from the chlorids of alkaline oralkaline-earth metals which consists in subjecting the chlorid insolution while owing continuously through each of a series of cells tothe action of an electric current ,between two electrodes in each cellinsulated from each other, but otherwise separated only by the liquid,imparting heat to the solution in each cell by suitable means suicieutto raise the temperature thereof toa degree suitable for thedecomposition of hypochlorites, and regulating the temperature of thesolution in each cell-by regulation of the owpof the solution throughthe cell, substantially as set forth.

Intestimony whereof I have hereunto set my hand in the presence of twosubscribing witnesses.

WM. T. GIBBS.

Witnesses! p M. H. PHELPS, A. L. KENT.

